Synchronous machine starting devices for starting synchronous machines such as generators and motors have been developed. Conventionally, a synchronous machine starting device uses a mechanical distributor that detects the position of a rotor of a synchronous machine, for example, by a proximity switch. However, the mechanical distributor is fragile and is susceptible to noise due to a large amount of wiring.
The inventors of the present application invented a synchronous machine starting device that does not require such a mechanical distributor, and filed it as an international patent application (see WO2010/038282 (PTL 1)). A synchronous machine starting device according to one embodiment described in PTL 1 will be described hereinafter.
This synchronous machine starting device includes a power conversion unit, an AC voltage detector, an AC current detector, a rotor position detection unit, and a power conversion control portion. The AC voltage detector and AC current detector detect three-phase AC voltage and three-phase AC current, respectively, supplied to or generated at an armature of a synchronous machine, and output the detection values to the rotor position detecting unit. The rotor position detection unit includes a zero cross detection unit, a first PLL (Phase Locked Loop) unit, a second PLL unit, and a selector circuit. The zero cross detection unit performs zero cross detection of AC voltage detected by the AC voltage detector. The first PLL unit outputs a position signal that is an AC signal having a prescribed frequency. Here, the prescribed frequency is a frequency corresponding to a predetermined rotational speed of the rotor during standby of the synchronous machine. The first PLL unit adjusts the phase of the position signal based on the detection signal received from the zero cross detection unit. The second PLL unit calculates an estimated phase indicating the rotor position of the synchronous machine by performing feedback operation so as to reduce an error of induction voltage of the armature, based on the detection values received from the AC voltage detector and AC current detector, and outputs a position signal obtained from the calculated estimated phase. The selector circuit selects, at the time of starting of the synchronous machine, the detection signal from the zero cross detection unit, the position signal from the first PLL unit, and the position signal from the second PLL unit in this order, and outputs the selected position signal as a rotor position signal indicating the rotor position of the synchronous machine.